This invention relates to flame-retardant polyphenylene ether resin compositions. More particularly, this invention relates to a flame-retardant composition (I) produced by adding a styrene type polymer to a polyphenylene ether and mixing the resultant resin composition with a phosphorus-containing compound; a flame-retardant composition (II) produced by adding a styrene type polymer to a polyphenylene ether having a styrene type compound graft-copolymerized thereto and mixing the resultant resin composition with a novel organic phosphorus-containing compound; and a flame-retardant composition (III) produced by mixing said flame-retardant composition with at least one compound selected from the group consisting of (a) aromatic organophosphorous acid esters and (b) aromatic organophosphorous acid esters and triazole ring-containing compounds.
In recent years, polyphenylene ether resins have come to have great attention because they have excellent mechanical properties, electrical properties, chemical resistance and thermal resistance, exhibit low hydroscopicity and enjoy high dimensional stability. Further, since polyphenylene ethers possess excellent flame retarding properties, they are rated as self-extinguishing and non-dripping by ASTM Testing Method D-635 and specification No. 94 of Underwriters' Laboratories (hereinafter abbreviated as "UL-94"). Polyphenylene ethers, however, have long had poor fabricability, which constitutes their gravest defect. As means for improvement in this respect, there have been suggested a number of methods resorting to the addition of styrene type polymers. For example, Japanese Patent Publication No. 17812/1968, Japanese Patent Publication No. 32774/1973, U.S. Patent No. 3,383,435, etc., disclose compositions containing polyphenylene ethers blended with styrene type polymers. There have also been suggested a number of methods resorting to graft polymerization of styrene type compounds. For example, Japanese Patent Publication No. 1210/1972, U.S. Pat. No. 3,664,977, Japanese Laid-open Patent Publication No. 98446/1974, U.S. Pat. No. 3,929,931, U.S. Pat. No. 3,586,736, U.S. Pat. No. 3,664,977 and U.S. Pat. No. 3,929,931 disclose resin compositions having styrene type compounds graft copolymerized to polyphenylene ethers.
The resin compositions having the fabricability of polyphenylene ethers improved as disclosed by these prior patent publications, however, have the disadvantage that they do not make materials suitable in regard to flammability for a wide range of industrial uses because the styrene type polymers incorporated therein possess neither self-extinguishing properties nor non-dripping properties and, upon ignition, they are completely burnt out.